Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$216.84	5.462%	$228.6838	$228.68	$228.70	$228.70
Purchase #2	$51.57	8.241%	$55.8199	$55.82	$55.80	$55.80
Purchase #3	$12.36	11.542%	$13.7866	$13.79	$13.80	$13.80
Purchase #4	$53.35	11.214%	$59.3327	$59.33	$59.35	$59.30
Purchase #5	$183.45	8.558%	$199.1497	$199.15	$199.15	$199.10
Purchase #6	$52.68	13.776%	$59.9372	$59.94	$59.95	$59.90
Purchase #7	$45.83	3.433%	$47.4033	$47.40	$47.40	$47.40
7 purchase totals =	$616.08		$664.1132	$664.11	$664.15	$664.00